During the 2017 growing season, the Nebraska Department of Agriculture received 90 claims of dicamba injury in non-Xtend soybeans. However, Nebraska Extension Educators compiled a total of 348 claims from across the state, representing approximately 50,000 acres of non-Xtend soybeans injured by dicamba (Amit Jhala, personal communication).

In summer 2017 we conducted a survey of Nebraska soybean farmers’ perceptions on dicamba use in Xtend soybeans. The survey was conducted in two formats:

Printed surveys were handed out during the 2017 Soybean Management Field Days, held at four major soybean growing areas of Nebraska (August 08-11 at North Platte, Ord, Auburn, and Tekamah, respectively).

An online survey linked from CropWatch was available from August 18 through September 18 via SurveyMonkey.

The survey was comprised of three main sections:

Demographics of participants

Outcomes from dicamba application in Xtend soybeans

Perceived dicamba injury in non-Xtend soybeans

The results presented here represent the opinions and observations of Nebraska farmers and not University of Nebraska-Lincoln weed scientists and Nebraska Extension educators. To avoid redundancy, only responses from those who described themselves as farmers were used. Results are expressed as a percentage of either total answers or total acres represented for each question (not every question was answered by all participants).

Survey Results

Demographic Information

312 farmers from 60 Nebraska counties participated in the survey, representing a total of 192,301 acres of soybeans grown in 2017 (Figure 1).

Of these, in 2017, 71% of soybean producers sprayed their own herbicide programs.

In 2017 19% of the total acres represented in the survey were planted with Xtend varieties. For 2018, farmers anticipate planting 52% of their soybean acres with Xtend varieties.

In 2017, 73% of the Xtend soybean acres were treated postemergence with dicamba. For 2018, farmers anticipate 88% of the Xtend soybean acres will be sprayed postemergence with dicamba.

Figure 1. Nebraska counties represented in the survey. 312 farmers from 60 Nebraska counties participated in the survey, representing a total of 192,301 acres of soybeans grown in 2017.

Outcomes from Dicamba Application in Xtend Soybeans in 2017

55%, 38%, and 7% of the surveyed Xtend soybean acres that were treated postemergence with dicamba were sprayed with Xtendimax, Engenia, and Fexipan, respectively. No farmer reported the use of a non-approved dicamba formulation for postemergence application in Xtend soybeans.

93% of farmers reported significant improvement in weed management with the use of the Xtend technology.

In terms of postemergence programs, 58% of Xtend acres were treated with either dicamba alone or dicamba in tank mix with glyphosate. The remaining 42% were treated with a more diversified postemergence program including additional herbicide sites of action.

18% of respondents reported that their dicamba application in Xtend soybeans injured neighboring non-Xtend soybean fields (volatility was believed to be the main cause of off-target dicamba movement followed by particle drift); 9% were not sure and 73% were confident that no injury was caused by their application.

The overall likelihood, based on survey responses, for dicamba injury in neighboring non-Xtend soybeans in 2017 increased when dicamba was sprayed late-June/July when compared to applications from May through mid-June (Figure 2).

Figure 2. Probability and frequency of dicamba injury in neighboring non-Xtend soybeans given dicamba application date in Xtend soybeans. Likelihood model (red line) was developed using farmers’ responses (YES or NO injury in neighboring non-Xtend soybeans after dicamba application in Xtend soybeans).

Perceived Dicamba Injury in Non-Xtend Soybeans in 2017

50% of respondents reported dicamba injury in their non-Xtend soybeans; however, the total injured acreage was 13%.

The suspected causes of injury were: tank-contamination (6%), off-target dicamba movement from application in Xtend soybeans (64%), and off-target dicamba movement from late applications in corn (30%). For off-target dicamba movement from applications in Xtend soybeans and corn, volatility was believed to be the main cause followed by particle drift.

93% of respondents who had non-Xtend soybeans injured by dicamba did not file a claim with the Nebraska Department of Agriculture.

Take-Home Messages from Survey Results

Farmers who adopted the technology in 2017 observed significant improvement in weed control.

Almost 60% of Xtend soybean acres represented in this survey were treated postemergence with dicamba alone or when tank-mixed with glyphosate. Glyphosate-resistant weeds are widespread across the soybean production areas of Nebraska and managing these troublesome weeds with dicamba alone is not a sustainable strategy from a herbicide-resistance management standpoint.

Most farmers spray their own herbicide programs; therefore, proper training on dicamba handling and application is crucial to minimize application errors. If applicators decide to buy and spray dicamba in Xtend soybeans in 2018, they must attend Auxin Herbicide Training. (More information on the training will be published in CropWatch in January.)

Off-target dicamba movement in Nebraska in 2017 was believed to occur not only from applications in Xtend soybeans, but also from applications in corn (most likely from late postemergence applications for control of common waterhemp and Palmer amaranth). Therefore, applicators should be mindful not only when spraying dicamba in Xtend soybeans but also in other crops.

Nebraska soybean farmers believe that volatility played an important role in off-target dicamba movement during the 2017 growing season.

Late postemergence applications of dicamba were more likely to result in non-Xtend soybean injury when compared to burndown and early postemergence applications.

Acknowledgements

We would like to acknowledge Keith Glewen (UNL Extension Educator), Lisa Jasa (CropWatch Editor), and Gustavo Vieira (UNL Visiting Undergraduate Student) for their assistance with the survey. A special thanks to all survey participants for their time answering the questions and providing us valuable feedback.